[llvm-dev] Runtime-configurable LLVM_DEFAULT_TARGET_TRIPLE by env var

[NAKAMURA Takumi via llvm-dev]

On Wed, May 3, 2017 at 9:49 AM Reid Kleckner <rnk at google.com> wrote:

> Hypothetically you could hack this in with our existing environment
> override option, CCC_OVERRIDE_OPTIONS, like so:
> ninja all
> export CCC_OVERRIDE_OPTIONS=#^--target=$triple
> # run lit tests
>

It's an option just in clang driver. It doesn't affect to other clang tools
(including libclang), and LLVM.

I'd rather not make a new, easier to use environment variable because it
> will encourage people to use it for production cross-compilation. The
> existing mechanism is probably good enough for testing purposes.
>

Agreed partially. I won't introduce such an option in release binaries.


> On Tue, May 2, 2017 at 5:26 PM, NAKAMURA Takumi via llvm-dev <
> llvm-dev at lists.llvm.org> wrote:
>
>> I have been working for extending test coverage for years.
>> Nowadays, I have several cross-testing (target != host). See
>> http://bb.pgr.jp/console
>> Each of them (test-*-linux) is doing;
>>
>>   - Assume a preceding builder passes with warming ccache.
>>   - All compilation units will hit ccache whenever the tree is built
>> before lit.
>>   - Almost all compilation units will hit ccache except for Host.cpp when
>> the tree is built with different LLVM_DEFAULT_TARGET_TRIPLE.
>>
>> FYI, I am doing a trick to let ccache recognize compilation units
>> identical for build.ninja;
>>
>>   $ sed -i -r 's=(-I|_COMPILER\S*
>> )/home/bb/\w[^/]*/llvm-project=\1../llvm-project=g' build.ninja
>>
>> In other words, testing builders have almost same build except for
>> Host.cpp.
>> I have to build the tree for each testing target.
>>
>> I propose an option to override LLVM_DEFAULT_TARGET_TRIPLE in run-time.
>> The change will be small but I wonder which option I could take.
>> Please let me know your suggestions.
>>
>> * Should it be configurable option?
>>
>> I think it shouldn't be required for release binaries, and it wouldn't be
>> required for most developers.
>> I think it may be off by default.
>>
>> * What is the name of environment variable?
>>
>> I suggest the name itself could be configurable.
>> If I would introduce the envvar name as "LLVM_TARGET", clang users would
>> complain why clang didn't have like "CLANG_TARGET".
>>
>>   $ cmake -DLLVM_DEFAULT_TARGET_ENVVAR_NAME=LLVM_TARGET
>>   $ LLVM_TARGET=i686-win32 bin/llvm-lit path/to/tests
>>
>> This feature may be disabled if LLVM_DEFAULT_TARGET_ENVVAR_NAME is blank.
>> I wonder the name LLVM_DEFAULT_TARGET_ENVVAR_NAME might be weird.
>> Better suggestions are welcome.
>>
>> As a future plan, I will implement, in Lit, run tests with the matrix of
>> triples,
>> like {arm|mips|i686|x86_64}-{darwin|linux|win32}.
>> Some of tests should be skipped if it isn't affected to default target
>> triple.
>> For example, FileCheck
>>
>> Regards, Takumi
>>
>> _______________________________________________
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>> llvm-dev at lists.llvm.org
>> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>>
>>
>
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